Phylogeography of Quercus aquifolioides provides novel insights into the Neogene history of a major global hotspot of plant diversity in south‐west China

Abstract

Aim Hotspots of biodiversity are often associated with areas that have undergone orogenic activity during recent geological history. Mountain uplifts are known to catalyse species radiation but their impact on evolutionarily stable taxa such as many trees remains little understood. The oak Quercus aquifolioides is endemic to yet widely distributed across the Hengduanshan Biodiversity Hotspot in the Eastern Himalayas. Here, we investigate how the region's Neogene and Quaternary history has driven the species' past population dynamics and the resulting extant patterns of intraspecific diversity.Location Hengduanshan Biodiversity Hotspot in SW China.Methods We sampled 58 populations throughout the species range and genotyped a total of 959 individuals at four chloroplast DNA fragments and 11 nuclear microsatellite loci. Phylogenetic reconstructions, molecular dating techniques and ancestral area reconstructions were used in combination with population genetic statistics to infer the biogeographical history of Q. aquifolioides. The phylogeographical study was complemented by a survey of fossil records and a niche modelling exercise.Results Combined molecular and fossil evidence indicates that Q. aquifolioides descended during the late Miocene from the central Qinghai-Tibet Plateau into Tibet and the western Sichuan Plateau, and from there, into the area of highest endemism in the Hengduan Mountains sensu lato. Great apparent population stability and a haplotype 'radiation' in this area contrasted with marked extinction-recolonization dynamics and reduced population diversity in Tibet. We found evidence for extremely limited seed gene flow but extensive pollen gene flow (global F ST : cpDNA = 0.98, nSSR = 0.07) with signals of asymmetric pollen dispersal from the Hengduan Mountains into Tibet. Main conclusionOur results provide insights of unprecedented detail into the ancient biogeographical history of the Hengduanshan Biodiversity Hotspot, suggesting that past environmental changes in the region may have catalysed radiative diversifications within species much in the same way as among species.

Concealed truth: Modeling reveals unique Quaternary distribution dynamics and refugia of four related endemic keystone Abies taxa on the Tibetan Plateau

“…Conversely, the other two Abies taxa expanded their populations in this area during the same period, because smooth fluctuations of temperature and precipitation were more important for them than were changes in other environmental variables (Table ). Analogous results have been reported for two other tree species at the TP, Taxus wallichiana and Quercus aquifolioides (Du et al, ; Yu, Zhang, Gao, & Qi, ). In the Northern Hemisphere, particularly in East Asia and western North America, the movement and shift of northern Abies taxa southward to the glacial region and the migration of southern Abies taxa northward to the interglacial region have been reported (Alba‐Sánchez & López‐Merino, ; Terhürne‐Berson, Litt, & Cheddadi, ).…”

“…Identification of Quaternary refugia is based on various forms of historical biogeographic evidence, particularly those derived from paleo‐ecological studies. Such evidentiary studies helped to identify glacial refugia in the TP over the most critical periods of the Pleistocene for exemplary taxa including Ginkgo biloba , Pedicularis longiflora , Primula secundiflora , evergreen oaks ( Quercus aquifolioides ), and Primula sikkimensis (Du et al, ; Gong, Chen, Dobes, Fu, & Koch, ; Wang, Gong, Hu, & Hao, ; Yang, Li, Ding, & Wang, ). Knowledge of Quaternary refuge distributions of species long ago (Cao et al, ), as well as remaining refuge distributions under current climate change conditions (Tinner & Valsecchi, ), can inform the future protection of Abies trees against climate change.…”

Warm–cold colonization: response of oaks to uplift of the Himalaya–Hengduan Mountains

“…, ; Du et al . ). In the divergence time estimation, the accurate, oldest known fossil of Quercus sect.…”

“…Phylogeographic research also provides evidence that the Hengduan Mountains is a distribution centre for Q. aquifolioides (Du et al . ). The distinctive distribution patterns span the HHM and eastern China, as well as the accurate fossil records (Fig.…”

Population genetic structure and adaptive differentiation of iron walnut Juglans regia subsp. sigillata in southwestern China

“…It is considered as a hot spot for vascular plant biodiversity (López‐Pujol, Zhang, Sun, Ying, & Ge, ; Myers, Mittermeier, Mittermeier, Da Fonseca, & Kent, ) and the core region of genetic diversity for many species (Brookfield, ). Of particular biogeographic interest are the Hengduan Mountains, which are located in the southeastern part of the Qinghai–Tibet Plateau (Du, Hou, Wang, Mao, & Hampe, ). This range includes mountains in Sichuan province, Yunnan province, and eastern Tibet Autonomous Region (Zhao, Gugger, Xia, & Li, ).…”